The present invention relates to intraocular lenses (IOLs). More particularly, the present invention relates to IOLs that provide accommodating movement in the eye.
The human visual system includes the eyes, the extraocular muscles which control eye position within the eye socket, the optic and other nerves that connect the eyes to the brain, and particular areas of the brain that are in neural communication with the eyes. Each eye forms an image upon a vast array of light sensitive photoreceptors of the retina. The cornea is the primary refracting surface which admits light through the anterior part of the outer surface of the eye. The iris contains muscles which alter the size of the entrance port of the eye, or pupil. The crystalline lens has a variable shape within the capsular bag, under the indirect control of the ciliary muscle. Having a refractive index higher than the surrounding media, the crystalline lens gives the eye a variable focal length, allowing accommodation to objects at varying distances from the eye.
Much of the remainder of the eye is filled with fluids and materials under pressure which help the eye maintain its shape. For example, the aqueous humor fills the anterior chamber between the cornea and the iris, and the vitreous humor fills the majority of the volume of the eye in the vitreous chamber behind the lens. The crystalline lens is contained within a third chamber of the eye, the posterior chamber, which is positioned between the anterior and vitreous chambers.
The human eye is susceptible to numerous disorders and diseases, a number of which attack the crystalline lens. For example, cataracts mar vision through cloudy or opaque discoloration of the lens of the eye. Cataracts often result in partial or complete blindness. If this is the case, the crystalline lens can be removed and replaced with an intraocular lens, or IOL.
While restoring vision, conventional IOLs have limited ability for accommodation (i.e., the focusing on near objects). This condition is known as presbyopia. To overcome presbyopia of an IOL, a patient may be prescribed eyeglasses. Alternative attempts in the art to overcome presbyopia focus on providing IOLs with accommodation ability. Accommodation may be accomplished by either changing the shape of the IOL, e.g., to become more convex to focus on near objects, or by moving the IOL along its optical axis.
IOLs which achieve accommodation by changing shape generally fall into one of two categories. In the first category, external means, such as magnetic or electric fields, inflation devices, or micromotors, are used to change the curvature of a deformable optic. In the second category, a force transfer assembly is provided for transferring the natural forces exerted by the eye to a composite optic including two or more portions with differing mechanical and/or optical properties.
Examples of the first category (i.e. externally actuated) shape-changing accommodating IOLs are found in Schachar U.S. Pat. No. 4,373,218, Kern U.S. Pat. No. 4,601,545, Pfoff U.S. Pat. No. 4,816,031, Wiley U.S. Pat. Nos. 5,066,301, 5,108,429, and 5,203,788, and Wiley et al. U.S. Pat. No. 5,171,266. The disclosures of each of these patents are incorporated herein in their entireties by reference.
Examples of the second category of shape-changing (i.e. naturally actuated) accommodating IOLs are found in Sulc et al. U.S. Pat. No. 4,994,083 and Turley U.S. Pat. No. 4,892,543. The disclosures of each of these patents are incorporated herein in their entirety by reference. Other examples of naturally actuated, shape-changing accommodating IOLs are described in co-pending, commonly assigned U.S. patent application Ser. Nos. 09/656,661, 09/657,251, and 09/657,325, all filed on Sep. 7, 2000, and in co-pending, commonly assigned U.S. patent application Ser. No. 09/855,331, filed May 15, 2001. The disclosures of each of these applications are incorporated herein in their entirety by reference.
Examples of axially movable accommodating IOLs are disclosed in Gwon et al. U.S. Pat. No. 6,176,878 and Laguette et al. U.S. Pat. No. 6,406,494. The disclosures of both these patents are incorporated herein in their entirety by reference.
IOLs which use primarily only one of the above mechanisms for accommodation have not been able to achieve the full add power required for a typical patient.
In view of the foregoing, it would be beneficial in the art, and there continues to be a need, to provide new IOLs with enhanced accommodation ability.